It is known that mono-1-olefins (α-olefins), including ethylene, can be polymerized with catalyst compositions employing titanium, zirconium, vanadium, chromium or other metals, impregnated on a variety of support materials, often in the presence of cocatalysts. These catalyst compositions may be useful for both homopolymerization of ethylene, as well as copolymerization of ethylene with comonomers such as propylene, 1-butene, 1-hexene, or other higher α-olefins. Therefore, there exists a constant search to develop new olefin polymerization catalysts, catalyst activation processes, and methods of making and using catalysts that will provide enhanced catalytic activities and polymeric materials tailored to specific end uses.
Linear low-density polyethylene (LLDPE) films, made by blown film or cast film processes, are widely utilized for packaging applications. Most packaging applications require either high transparency (low haze and high clarity), or either no or low transparency (high haze and low clarity). While high transparency is often achieved through resin design, low transparency is typically achieved through the addition of coloring agents or fillers such as titanium oxide and the like.
What are needed are new resins that provide films of high opacity (low transparency), without the need for adding coloring agents or fillers in substantial amounts. What are also needed are catalyst compositions and methods that afford such resins and films.